SERIES FINALE: Last night, Stephen Colbert provided a very fitting farewell to his Colbert Report, gathering dozens of favorite guests on stage for a group sing-along before flying off to immortality on Santa’s sleigh. Tonight, Craig Ferguson ends his 10-year reign as the host of The Late Late Show, CBS’s follow-up to Late Show with David Letterman – and does it by featuring, as his final guest, Letterman’s one-time late-night rival, Jay Leno. Doubtlessly, there’s a message there – and there’s also likely to be a message, or at least an homage, in the show’s closing minutes. For a decade, Ferguson has been increasingly loose and impromptu with his opening monologues and his interviews with guests – but expect him to go out as Colbert did, with an involved and ambitious final sequence. These guys not only have am attuned sense of when to exit – but how.